Satin nickel electroplating techniques that include homogenization units

ABSTRACT

Certain example embodiments of this invention relate to improved electroplating techniques. More particularly, certain example embodiments of this invention relate to electroplating techniques that incorporate a homogenization unit to help maintain an emulsion within an electrolyte solution (e.g., a nickel electrolyte solution) used in creating a finish (e.g., a satin nickel finish) in an electroplating process. By varying the operational characteristics of the unit (including, for example, pressure, velocity, pore size, ultrasound wave frequency, sonication time, etc.), it becomes possible to control the emulsion particle size distribution so as, for example, increase or decrease the diameter of such particles and thereby resulting in a deposit with a desired surface topography. It will be appreciated that the variations in size will cause variation in surface topography which, in turn, will change the surface appearance.

FIELD OF THE INVENTION

Certain example embodiments of this invention relate to improved electroplating techniques. More particularly, certain example embodiments of this invention relate to electroplating techniques that incorporate a homogenization unit to help maintain a stable colloidal system (e.g., an emulsion or dispersion) within an electrolyte solution (e.g., a nickel electrolyte solution) used in creating a finish (e.g., a satin nickel finish) in an electroplating process. The homogenization unit of certain example embodiments advantageously helps extend the life of the electroplating bath before articles with undesirable appearances are formed, while also reducing the amount of additive used in the overall electroplating process.

BACKGROUND AND SUMMARY OF EXAMPLE EMBODIMENTS OF THE INVENTION

A number of electroplating processes, including those used for creating satin nickel finishes, are known in the art. See, for example, U.S. Pat. Nos. 7,361,262; 6,306,275; 5,897,763; and 3,839,165, the entire contents of each of which are hereby incorporated herein by reference.

In nickel electroplating, one generally tries to achieve a uniform deposit in terms of surface topography, which generally helps to provide an aesthetically desirable, uniform appearance that typically is bright. A nickel coating with a satin finish is used in connection with a number of different applications, e.g., because of its decorative appearance and low glare. Typical applications include, for example, automotive parts and trim pieces (such as radiator grilles, door handles, etc.), housings and trim pieces for various electronic devices (such as mobile telephones, cameras, etc), furniture components, and/or the like.

Some forms of satin nickel electroplating generally involve creating an emulsion in a nickel electrolyte solution, typically in connection with a single supplier-provided additive component. In order to achieve an acceptable roughness depth for the deposited coating, the additive is to be dispersed throughout the electrolyte bath in the form of finely divided particles or micelles. A conventional, freshly prepared bath electrolyte typically will exhibit the desired finely divided particle dispersion. However, after some period of time, the finely divided particles or micelles will coalesce or agglomerate into larger particles or micelles. As the average particle or micelle size and/or particle distribution size changes, the roughness depth may increase and therefore the appearance of the deposited coatings may change in an undesirable and/or uncontrolled manner. The increase in roughness depth may be uniform or non-uniform across the substrate. The increase in roughness depth leads to undesirable appearances in terms of unexpected or undesirable coloration, bright spots or bands and/or other non-uniformities, etc. The produced articles generally are unacceptable at this point.

The stability of the finely dispersed particles of additive may be improved, for example, by adding stabilizing wetting agents, such as, for example, branch chained alkyl sulfates or sulfonates. This may delay the agglomeration of the particles. However, the roughness depth will still continue to increase to an unacceptable level, just at a potentially slower rate. Ultimately, an unacceptable roughness depth will occur, and the produced articles likely will be rejected because of their generally unacceptable appearance. Furthermore, the assignee of the instant invention has discovered that temperature variance sometimes may cause the surface activating agents to precipitate out from the electrolyte solution, causing the coalescence of dispersed particles of additive. Bypass circulation of the solution may be used in order to help avoid approaching or exceeding the cloud point of surfactants so that they are more likely to remain in solution.

To improve the process, a so-called “bleed and feed” technique has been developed and implemented. In general, this process attempts to separate or filter out the agglomerated emulsion particles from the “good emulsion,” and then “add back” the additive. More particularly, in a typical “bleed and feed” process, a portion of the electrolyte is removed from the electroplating bath. The additive is separated or filtered out from the electrolyte that was removed from the electroplating bath. Additional additive is then added to the flow, and the electrolyte with the new additive is returned to the electroplating bath.

This “bleed and feed” technique has been found to help extend the life of the bath. For example, the assignee has found that bath life can be increased to 2 to 2.5 days before yields decreased and the process tank had to be removed from production for cleaning and maintenance.

Although the “bleed and feed” technique is advantageous, it will be appreciated that it would be desirable to extend the life of the bath yet further. It also will be appreciated that it would be desirable to reduce the need for the complete removal of the agglomerated particles and the adding back of new additive, at least from cost and ease-of-administration perspectives. Similar observations apply with the current need to at least temporarily remove the process tank for cleaning and maintenance. Indeed, agglomerated particles have the tendency to stick to tank walls and anode bags and may disengage from them during the production leading to defects such as bright spots on the parts by sticking to their surface.

Certain example embodiments of this invention help to further improve on current electroplating (e.g., satin nickel electroplating) techniques by providing the above-described and/or other advantageous aspects.

In certain example embodiments of this invention, a satin nickel electroplating system is provided. A satin chemistry process tank receives a flow of a solution including an emulsion to form a bath used in electroplating an article. A satin dosing system is configured to add further emulsion to the flow at a controlled rate. A flow meter is provided between the satin dosing system and the satin chemistry process tank. A homogenization unit is configured to break down agglomerates formed in the electroplating system and/or the bath such that the bath and the emulsion in the tank are substantially free from agglomerates larger than 40 microns, more preferably 25 microns, and still more preferably 10-15 microns in diameter.

In certain example embodiments of this invention, an electroplating system is provided. A process tank holds an electroplating bath (e.g., including the satin nickel or other desired chemistry). A dosing system is configured to provide an additive used for the electroplating bath. A flow meter provided between the process tank and the dosing system is configured to regulate the flow of the additive into the bath, with the additive at least initially provided as a substantially homogenized emulsion or colloidal solution. At least one homogenization unit (e.g., provided between the process tank and the dosing system) is configured to break down any agglomerates of particles of the additive of a predetermined size that form over time, with the predetermined size being 40 microns in diameter.

In certain example embodiments of this invention, a method of making an electroplated article is provided. An electroplating system is provided, with the electroplating system including a process tank, a dosing system configured to provide an additive used in an electroplating bath, a flow meter provided between the process tank configured to regulate the flow of the additive into the bath, and at least one homogenization unit (e.g., provided between the process tank and the dosing system). The electroplating bath is provided to the process tank, with the additive at least initially being a substantially homogenized emulsion. Via the homogenization unit, any agglomerates of particles of the additive of a predetermined size that form over time are broken down, with the predetermined size being 40 microns, more preferably 25 microns, and still more preferably 10-15 microns in diameter. The article is electroplated such that a substantially uniform finish (e.g., with the desired color and overall appearance) is provided thereon.

The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages may be better and more completely understood by reference to the following detailed description of exemplary illustrative embodiments in conjunction with the drawings, of which:

FIG. 1 is an example schematic view of an improved satin nickel electroplating system including a homogenization unit in accordance with an example embodiment; and

FIG. 2 is a flowchart showing an illustrative process for operating an improved satin nickel electroplating system and/or making an article using the same, in accordance with an example embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Certain example embodiments incorporate a homogenization unit. The homogenization unit of certain example embodiments helps to create an emulsion that is more stable over time by reducing and/or redistributing agglomerated emulsion particles. By varying the operational characteristics of the unit (including, for example, pressure, velocity, pore size for membrane homogenizers (MHs), sound wave frequency and sonication time for ultrasound disruptors (UDs), etc.), it becomes possible to control the emulsion particle size so as, for example, increase or decrease the diameter of such particles and thereby resulting in a deposit with a desired surface topography. It will be appreciated that the variations in size will cause variation in surface topography which, in turn, will change the surface appearance. For instance, by reducing the agglomeration effect, it is possible to reduce (and sometimes even completely eliminate) the need for “bleed and feed” and/or other filtration systems while still increasing bath production life.

An emulsion initially added to an electrolyte solution typically is at least initially stable in the sense that the small particles included in the emulsion typically are substantially homogenously distributed. Because the particles are small, the entire electroplating bath can stay relatively stable in this “neutral state” for a period of time. Unfortunately, over time, the small particles in the emulsion will clump together, forming an unstable emulsion that has agglomerated particles that are not miscible with the overall solution.

In an attempt to obtain a consistent and substantially uniform emulsion over the plate in the satin chemistry process tank, and to keep it stable over time, the assignee of the instant invention has implemented a particular “bleed and feed” approach. This approach attempts to compensate for the fact that current techniques are unable to precisely control the emulsion particle size directly and instead relies in part on the addition of new and/or filtered micro-emulsion additives. More particularly, the “bleed and feed technique” implemented by the assignee involves running a filtering process to remove at least a portion of the additive, including those particles that have agglomerated into non-miscible clumps, and adding into the bath filtered and/or fresh additive. The adding occurs periodically, whereas the filtering occurs substantially continuously. It will be appreciated that the filtering out of the agglomerated particles and/or the adding back of the new additive could be performed continuously or periodically in different implementations.

Unfortunately, however, it is not always easy to add back in filtered and/or new additive. For instance, it is difficult to monitor the agglomerations directly in the bath and/or following the filtering. Similar difficulties arise in monitoring the concentration of the additive in the bath. Thus, questions arise regarding how fast to “turn-over” the bath (such as how fast and when to temporarily halt the electroplating, discard the current bath, and create a brand new bath), how fast and when to begin adding new and/or filtered material, etc. It also is sometimes difficult to control the adding back and/or adding of new additives. These variations sometimes lead to inconsistent results, which may be caused by inconsistencies in the percentage of additive present in the overall bath.

However, as indicated above, certain example embodiments may supplement or completely supplant such “bleed and feed” and/or other filtering approaches by means of a homogenization process using, for instance, a homogenization, unit, pump, and/or tank. The homogenization techniques of certain example embodiments may use a pump and/or tank to create pressure and/or velocity differentials to create a flow (e.g., a turbulent, laminar, or other flow) within the emulsion. The homogenization techniques of certain example embodiments may in addition or in the alternative vary pore size for membrane homogenizers (MH), sound wave frequency and sonication time for ultrasound disruptors (UD), and/or the like. This may, in turn, homogenize the emulsion by dispersing the particles therein, creating a dispersed phase that is similar to the initial dispersed phase. Example homogenizers include systems commercially available from Sonic Mixing, APV Homogenizers, BEE International and others.

It will be appreciated that the dispersed phase may be substantially homogenized. However, this does not mean that the solution will be completely free from all agglomerations. Rather, the solution may in certain example instances be free from agglomerates that could or would cause a visible distortion on the end product. Thus, a stable, substantially homogenized solution may be produced provided that agglomerates do not exceed a predetermined mean or absolute size or size distribution.

In this regard, the Pearlbrite K6 additive used by the assignee is believed to have a mean particle size of about 2-4 microns (e.g., in diameter). It has been found that agglomerates of about 40 microns will cause severe bright spots, and that agglomerates of about 25 microns may produce visible hair-sized discolorations and/or non-uniformities that are visible and noticeable. Thus, certain example embodiments provide a substantially homogenized solution in which agglomerated particles are less than about 40 microns, more preferably less than about 25 microns, and still more preferably less than about 15 microns. In certain example instances, it may be desirable to allow agglomerations of no more than about 10 microns. These values may be absolute values for all particles or mean particle size values. Of course, it will be appreciated that these are example ranges and that other sizes, size distributions, and/or ranges or sub-ranges also may be used in connection with different example embodiments.

The turbulent, laminar, or other flow may help break down the particles. In this regard, the homogenization unit may in certain example embodiments be run substantially continuously or periodically to break down large particle agglomerates. Imaging and/or filtering means may be provided so as to optically, physically, and/or otherwise determine particle size for a predefined amount of the solution and, when appropriate, increase or decrease the flow caused by the homogenization unit to cause more agglomerations to be broken up and/or to allow to be formed (e.g., within the overall tolerance).

Certain example embodiments advantageously extend the life of the bath. This, in turn, may provide cost savings from less turn-over and less downtime associated therewith, as well as the reduced need to continue dosing with new additive. During the course of a single bath, for example, better and/or more uniform colorations may be provided as a result of the fewer interruptions involved in the laying down of the nickel and the fewer peaks and valleys created by the agglomerates.

FIG. 1 is an example schematic view of an improved satin nickel electroplating system including a homogenization unit in accordance with an example embodiment. A satin chemistry process tank and/or overflow weir of the tank 102 is provided. This process tank includes the mixture and is oriented proximate to the plate (not shown) used in forming an electroplated finish (e.g., a satin nickel finish) on a substrate. The flow of material continues to an optional filtration system 104. The optional filtration system 104 may be one of the above-described and/or other “bleed and feed” type filtration systems, or may simply attempt to filter out agglomerates larger than a predetermined size. The filtration system may in addition or in the alternative filter out other depleted chemicals from the electroplating bath. Regardless of whether the optional filtration system 104 is provided, a homogenization unit 106 is present to create a turbulent flow and break up agglomerates. The turbulent, laminar, or other flow (e.g., related to process parameters such as, for example, pressure and velocity) preferably is sufficient to break up agglomerates such that any agglomerates are no larger than 40 microns, more preferably no larger than about 25 microns, and still more preferably no larger than about 15. microns. In certain example instances, the homogenization unit may even provide a flow sufficient to break up any agglomerates such that the solution is substantially free from agglomerations greater than about 10 microns in size. Of course, it will be appreciated that these are example ranges and that other sizes, size distributions, and/or ranges or sub-ranges also may be used in connection with different example embodiments. The flow may be temporarily halted during processing in the homogenization unit 106, which itself may run continuously, periodically, or on an as-needed basis. For example, the homogenization unit 106 when errors are detected by human operators (e.g., as in the case of visible defects in the article) or by optical and/or mechanical means (e.g., agglomerates are detected in excess of a predetermined threshold). Appropriate optical sensors, mechanical filters, and/or the like may be provided for these and/or other purposes in example embodiments of this invention.

In an example implementation, the optional filtration system 104 may include two main tanks sized to process 200% of the tank volume per hour at a maximum pressure of 0.5 bar. The piping and filter volume may be sized to allow for, for example, 3000-7500 gal/hour. A commercially available Mefiag filter capable of processing at least about 40 sq. feet per 1000 gal total solution volume may serve such example purposes.

The additive may need to be introduced from time-to-time as a natural result of the use of the same, e.g., in the satin chemistry process tank as a part of the electroplating process. The additive also may need to be added back in the event of a “bleed and feed” and/or or other optional filtration approach. Accordingly, a satin dosing system 108 may be provided. The satin dosing system 108 may provide small injections continuously, periodically, or on an as-needed basis to replenish any losses. Preferably, the satin dosing system will be able to hold the concentration of the additive in the solution substantially constant and, together with the homogenization unit, the solution as a whole may remain substantially homogenized. The satin dosing system 108 also may help change dosages quickly, e.g., when a single line is changed from producing a first product to a second product. The flow meter 110 also may help to provide a steady flow of material back to the satin chemistry process tank 102.

It will be appreciated that the homogenization unit may be provided elsewhere in the system shown in FIG. 1. In addition, or in the alternative, certain example embodiments may incorporate a membrane homogenizer (MH). An MH may be provided, for example, before the diluted additive is added to the electroplating bath in order to help create particles of a certain size prior to the addition. In certain example embodiments, in addition or in the alternative, an ultrasound disruptor (UD) may be provided, e.g., in the bath and/or a high pressure homogenizer may be provided between the process tank and the dosing system. It will be appreciated that these and/or other homogenization subsystems may be provided at any suitable location in the overall system and that certain example embodiments may incorporate one or more of each of the above-listed and/or other homogenization subsystems. Thus, for example, although certain example embodiments may include a UD in the bath and/or an MH prior to addition, other arrangements are also possible in different embodiments.

Preferably, the bath in the satin chemistry process tank is stable over a period of at least about 2 days, more preferably at least about 2.5 days, and sometimes even for at least about 3 days.

FIG. 2 is a flowchart showing an illustrative process for operating an improved satin nickel electroplating system and/or making an article using the same, in accordance with an example embodiment. An electroplating system is provided in step S201. The electroplating system includes a process tank, a dosing system configured to provide an additive used in an electroplating bath, a flow meter provided between the process tank (e.g., as shown in FIG. 1), a flow meter configured to regulate the flow of the additive into the bath, and a homogenization unit provided (e.g., between the process tank and the dosing system). As indicated above, certain example embodiments may include a UD in the bath and/or an MH prior to addition, although other arrangements are also possible in different embodiments. In step S203, the electroplating bath is provided to the process tank, with the additive at least initially being a substantially homogenized emulsion. In step S205, via the homogenization unit, any agglomerates of particles of the additive of a predetermined size that form over time are broken down. As indicated above, the predetermined size preferably is 40 microns in diameter, more preferably 25 microns, still more preferably 15 microns in diameter, and sometimes even 10 microns in diameter. Of course, it will be appreciated that these are example ranges and that other sizes, size distributions, and/or ranges or sub-ranges also may be used in connection with different example embodiments. The article is electroplated in step S207. This example process may be repeated for any number of articles provided that the bath is stable, e.g., that substantially no particles at or above the predetermined size would be on the plate and/or transferred to the article.

Optionally, filtering may be provided such that, for example, at least some agglomerates larger than the predetermined size are filtered out and, correspondingly, a further amount of the additive is provided to help compensate for the filtered out agglomerates.

Although certain example embodiments have been described as breaking down particles having a certain “diameter,” it will be appreciated that the agglomerates may form from multiple particles in clumps that are not perfectly spherical or circular or ovular in cross section. Thus, the term “diameter” should not be interpreted as pertaining to perfectly formed spheres or the like and instead should be interpreted as referring to a general dimensional measurement of clumps of particles.

Although certain example embodiments have been described in relation to a satin nickel finish, it will be appreciated that other finishes may be provided. Such finishes may incorporate so-called “glare free” or low glare metals other than, or in addition to nickel. Similarly, finishes other than “satin” finishes may be provided in connection with different embodiments of this invention. Other matte finishes may include, for example platinum finishes or different finishes using metals other than nickel.

It will be appreciated that certain example embodiments may use a homogenizer unit in combination with a low glare or so-called “glare free” metal electroplating baths, e.g., in order to obtain a more controllable system that provides high reproducibility, low scrap, and reduced costs associated with waste and supply chemicals. The techniques described herein also are advantageous from the standpoint that the working parameters of the homogenizer unit(s) may be adjusted to change finishes, obtain new finishes, etc.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

1. A satin nickel electroplating system, comprising: a satin chemistry process tank to receive a flow of a solution including an emulsion to form a bath used in electroplating an article; a satin dosing system configured to add further emulsion to the flow at a controlled rate; a flow meter provided between the satin dosing system and the satin chemistry process tank; and a homogenization unit configured to break down agglomerates formed in the electroplating system and/or the bath such that the bath and the emulsion in the tank are substantially free from agglomerates larger than 25 microns in diameter.
 2. The system of claim 1, wherein the homogenization unit is located upstream of the satin dosing system.
 3. The system of claim 1, wherein the homogenization unit is operable to provide a flow so as to break down substantially all agglomerates larger than 15 microns in diameter.
 4. The system of claim 1, wherein the homogenization unit is operable to provide a flow so as to break down substantially all agglomerates larger than 10 microns in diameter.
 5. The system of claim 1, wherein the bath in the satin chemistry process tank is stable over a period of at least about 2 days.
 6. The system of claim 1, wherein the bath in the satin chemistry process tank is stable over a period of at least about 2.5 days.
 7. The system of claim 1, wherein the homogenization unit is configured to run continuously.
 8. The system of claim 1, wherein the homogenization unit is configured to run when a sensor detects agglomerates larger than a predetermined threshold.
 9. The system of claim 1, further comprising a filtration system configured to filter out at least some agglomerates.
 10. An electroplating system, comprising: a process tank for holding an electroplating bath; a dosing system configured to provide an additive used for the electroplating bath; a flow meter provided between the process tank and the dosing system configured to regulate the flow of the additive into the bath, the additive at least initially provided as a substantially homogenized emulsion or colloidal solution; and at least one homogenization unit configured to break down any agglomerates of particles of the additive of a predetermined size that form over time, the predetermined size being 40 microns in diameter.
 11. The system of claim 10, wherein the predetermined size is 25 microns in diameter.
 12. The system of claim 10, wherein the predetermined size is 15 microns in diameter.
 13. The system of claim 11, wherein the homogenization unit is configured to run continuously.
 14. The system of claim 11, wherein the homogenization unit is configured to run when a sensor detects agglomerates larger than the predetermined size.
 15. The system of claim 11, further comprising a filtration system configured to filter out at least some agglomerates and/or other depleted chemicals from the electroplating bath.
 16. A method of making an electroplated article, the method comprising: providing an using an electroplating system including a process tank, a dosing system configured to provide an additive used in an electroplating bath, a flow meter provided between the process tank and the dosing system configured to regulate the flow of the additive into the bath, and at least one homogenization unit; providing the electroplating bath to the process tank, wherein the additive is at least initially as a substantially homogenized emulsion; breaking down, via the homogenization unit, any agglomerates of particles of the additive of a predetermined size that form over time, the predetermined size being 25 microns in diameter; and electroplating an article such that a substantially uniform finish is provided thereon.
 17. The method of claim 16, wherein the predetermined size is 15 microns in diameter.
 18. The method of claim 16, wherein the homogenization unit is configured to run continuously.
 19. The method of claim 16, further comprising detecting agglomerates larger than the predetermined size and running the homogenization unit.
 20. The method of claim 16, further comprising: filtering out at least some agglomerates larger than the predetermined size; and providing a further amount of the additive to compensate for the filtered out agglomerates. 